This invention relates generally to storage and containment of devices used in conjunction with radioactivity monitoring and measurement. In particular, this invention relates to a storage device for radon gas detectors.
Radon gas is a naturally occurring radioactive noble gas that results from the decay of radium 226. It is long been recognized that exposure to radon gas (and radon gas "daughters" that occur as a result of radon gas decay) can pose a significant health hazard. Although testing for radon gas has been done for many years, until relatively recently, concern over exposure to radon gas was primarily associated with workers in the uranium mining industry or others whose work brought them in contact with uranium ore. In recent years, it has been recognized that radon gas can seep out of the ground through building foundations and can accumulate inside the buildings. When radon gas accumulates in a human environment, it is inhaled thereby exposing the lungs to radioactivity. The health hazards of radon gas exposure are associated with the increased likelihood for the development of lung cancer that may not occur until 10 to 20 years or more after exposure. As a consequence, it is now considered that naturally occurring radon gas can pose a significant health hazard to the general population. The United States Environmental Protection Agency (USEPA) estimates that as many as 20,000 deaths occur each year as a result of exposure to radon gas. The Department of Energy supports the study of radon gas measurement and detection through its Office of Remedial Action and Waste Technology.
Because of the present awareness of the health hazards associated with exposure to radon gas, widespread testing programs have been undertaken and further testing programs are planned. This testing includes buildings such as homes, schools and offices. To achieve widespread testing, it is recognized that many samples must be obtained. In fact, it is often considered appropriate to obtain several samples of a single building from different locations within the building. The testing for radon gas is normally performed by placement of detector devices in the location to be tested. These detectors typically contain an alpha track registration material which is sensitive to the radioactivity associated with radon gas. After placement of the detectors in the building being tested for an established period of time, typically on the order of several weeks to several months, the detectors are removed from the building and conveyed to a laboratory. At the laboratory, the detectors are analyzed with suitable equipment for the detection and measurement of radon gas. From this analysis a determination of the presence and concentration of radon gas in the building tested can be inferred. Accurate measurement of radon gas with the scheme described above is complicated by several factors. First of all, radon gas is widely present in the earth's environment and exists extensively in the background. Also, radon gas tends to diffuse so that a sampling scheme must take this into account. Also, when radon gas is sampled indoors, the degree to which the building is airtight (i.e., resistant to outside air exchange) can highly influence the radon gas measured.
Even if the above concerns regarding sampling are adequately addressed, other factors can be encountered that result in invalid data. One factor that can introduce significant errors into the sampling is contamination of the detectors. Normally, to obtain a sample, a detector which includes a sealed container containing a medium that is sensitive to radon gas (e.g. the alpha track registration material) is exposed to the air at the location to be tested for a period of time. After this period of time, the container is resealed and conveyed to a laboratory for analysis. It can be appreciated that it is essential that the detectors are not exposed to the air or any other potential source of contaminating radioactivity either before the sampling takes place or after the sampling during the time the detector is being conveyed to the laboratory for analysis. For this reason, detectors include airtight containers made of aluminized mylar in which the detectors can be sealed. Aluminized mylar is necessary because radon gas can diffuse through many types of ordinary plastics. If the aluminized mylar seal is breached either before or after the detector is installed in the test location, the detector can become contaminated and the months of testing invalidated. In addition, even though the containers containing the detectors are each individually sealed, since it is often the case that the sampling is done by persons without scientific or technical training, it is possible that leaks or faulty sealing can occur as a result of inexperienced handling. Moreover, if the detectors are stored for a time, such as during transit or while awaiting analysis in the laboratory, the possibility exists that the airtight seals on the containers may develop leaks thereby rendering the samples invalid.
At the present time there are no commercially available containment devices for the short or long term storage of radon gas detectors. If any attempt at preventing radioactive contamination of such detectors is made at all, it is done on an individual basis and without uniform standardized procedures.
Accordingly, it is an object of the present invention to provide an apparatus for the short and long term storage of radon gas detectors in a nearly radon free environment.
It is another object of the present invention to provide a device that provides for the storage of radon gas detectors in a radon free environment in an economical and efficient manner.
It is yet another object of the present invention to provide an apparatus for the storage of radon gas detectors that complements existing sealing schemes for radon gas detectors, such as aluminized mylar wrappers.
It is another object of this invention to provide an apparatus for the short and long term storage of radon gas detectors that provides a uniform, standardized method and that affords a high degree of protection from contamination.
It is yet still another object of this invention to provide both an active and passive scheme for the storage of radon gas detectors.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.